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Multilevel Structural equation models are most often estimated from a frequentist framework via maximum likelihood. However, as shown in this article, frequentist results are not always accurate. Alternatively, one can apply a Bayesian approach using Markov chain Monte Carlo estimation methods. This simulation study compared estimation quality using Bayesian and frequentist approaches in the context of a multilevel latent covariate model. Continuous and dichotomous variables were examined because it is not yet known how different types of outcomes—most notably categorical—affect parameter recovery in this modeling context. Within the Bayesian estimation framework, the impact of diffuse, weakly informative, and informative prior distributions were compared. Findings indicated that Bayesian estimation may be used to overcome convergence problems and improve parameter estimate bias. Results highlight the differences in estimation quality between dichotomous and continuous variable models and the importance of prior distribution choice for cluster-level random effects. 相似文献
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1 Introduction It is i mportant to study polymerization mechanisminpolymerization engineering. Obtaining kinetic data isthe key step for establishing polymerization mechanismand understanding elementary reactions . The kineticdata contains two groups of data ,i.e.,the rate andreaction order .The rate ,especially the rate constant ,is i mportant and to be esti mated assuming that the or-der of the reactionis known.Furthermore ,esti mationof rate constants for polymerization is an active anddif… 相似文献
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A new item parameter replication method is proposed for assessing the statistical significance of the noncompensatory differential item functioning (NCDIF) index associated with the differential functioning of items and tests framework. In this new method, a cutoff score for each item is determined by obtaining a (1 −α) percentile rank score from a frequency distribution of NCDIF values under the no-DIF condition by generating a large number of item parameters based on the item parameter estimates and their variance-covariance structures from a computer program such as BIILOG-MG3. This cutoff for each item can be used as the basis for determining whether a given NCDIF index is significantly different from zero. This new method has definite advantages over the current method and yields cutoff values that are tailored to a particular data set and a particular item. A Monte Carlo assessment of this new method is presented and discussed. 相似文献
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概述了蒙特卡罗方法的产生与发展，阐述了蒙特卡罗方法的基本特点，最后就蒙特卡罗方法在辐射剂量计算上的应用进行了讨论。 相似文献
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蒙特卡罗方法是一个以概率模型为基础,利用计算机通过多次反复模拟实验完成问题求解的一种数值计算方法。它特别适用于用传统的解析法难以解决甚至是无法解决的问题。文章主要介绍蒙特卡罗方法及基本原理,并通过实例说明蒙特卡罗方法在数学建模中的应用。 相似文献
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在多源理想气体模型的框架内,用解析和蒙特卡洛两种方法计算分析了中能重离子碰撞中末态核碎片的方位角分布和椭圆流对横动量的依赖关系,并由此分析了末态核碎片的各向异性分布特征。对计算结果与同位旋依赖的的量子分子动力学(ISQMD)模型的计算结果进行了比较,发现二者基本符合。 相似文献
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改进粒子滤波在被动目标跟踪中的应用 总被引：3，自引：0，他引：3
As a new method for dealing with any nonlinear or non-Ganssian distributions, based on the Monte Carlo methods and Bayesian filtering, particle filters （PF） are favored by researchers and widely applied in many fields. Based on particle filtering, an improved extended Kalman filter （EKF） proposal distribution is presented. Evaluation of the weights is simplified and other improved techniques including the residual resampling step and Markov Chain Monte Carlo method are introduced for target tracking. Performances of the EKF, basic PF and the improved PF are compared in target tracking examples. The simulation results confirm that the improved particle filter outperforms the others. 相似文献
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One challenge in mediation analysis is to generate a confidence interval (CI) with high coverage and power that maintains a nominal significance level for any well-defined function of indirect and direct effects in the general context of structural equation modeling (SEM). This study discusses a proposed Monte Carlo extension that finds the CIs for any well-defined function of the coefficients of SEM such as the product of k coefficients and the ratio of the contrasts of indirect effects, using the Monte Carlo method. Finally, we conduct a small-scale simulation study to compare CIs produced by the Monte Carlo, nonparametric bootstrap, and asymptotic-delta methods. Based on our simulation study, we recommend researchers use the Monte Carlo method to test a complex function of indirect effects. 相似文献
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Assessment of Differential Item Functioning Under Cognitive Diagnosis Models: The DINA Model Example 
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下载免费PDF全文 The assessment of differential item functioning (DIF) is routinely conducted to ensure test fairness and validity. Although many DIF assessment methods have been developed in the context of classical test theory and item response theory, they are not applicable for cognitive diagnosis models (CDMs), as the underlying latent attributes of CDMs are multidimensional and binary. This study proposes a very general DIF assessment method in the CDM framework which is applicable for various CDMs, more than two groups of examinees, and multiple grouping variables that are categorical, continuous, observed, or latent. The parameters can be estimated with Markov chain Monte Carlo algorithms implemented in the freeware WinBUGS. Simulation results demonstrated a good parameter recovery and advantages in DIF assessment for the new method over the Wald method. 相似文献
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This paper presents a new approach to parallelize 3D lattice Monte Carlo algorithms used in the numerical simulation of polymer on ZiQiang 2000-a cluster of symmetric multiprocessors(SMPs).The combined load for cell and energy calculations over the time step is balanced together to form a single spatial decomposition.Basic aspects and strategies of running Monte Carlo calculations on parallel computers are studied.Different steps involved in porting the software on a parallel architecture based on ZiQiang 2000 running under Linux and MPI are described briefly.It is found that parallelization becomes more advantageous when either the lattice is very large or the model contains many cells and chains. 相似文献
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用计算机模拟薄膜生长过程的KMC方法 总被引：1，自引：0，他引：1
以有表面活性剂介入的Cu薄膜为例,用Kinetic Monte Carlo方法对薄膜生长的随机过程进行了计算机模拟,并对所提出的模型和Kinetic Monte Carlo算法进行了详尽描述．在实现动力学生长过程及物理模型向计算机语言及算法的转化过程中,不仅构建了模拟薄膜生长过程的主体流程图,并且将主体流程图分解成了原子吸附事件流程图、原子迁移事件过程流程图、“小事件”列表刷新流程图和事件列表刷新示意图四个部分,分别对其进行说明和阐述．可以看出在薄膜领域中,计算机模拟在理论和实验这两方面的研究中都发挥了重要作用,Kinetic Monte Carlo方法也已经成了解决薄膜生长相关问题的必要工具． 相似文献
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Despite its importance to structural equation modeling, model evaluation remains underdeveloped in the Bayesian SEM framework. Posterior predictive p-values (PPP) and deviance information criteria (DIC) are now available in popular software for Bayesian model evaluation, but they remain underutilized. This is largely due to the lack of recommendations for their use. To address this problem, PPP and DIC were evaluated in a series of Monte Carlo simulation studies. The results show that both PPP and DIC are influenced by severity of model misspecification, sample size, model size, and choice of prior. The cutoffs PPP < 0.10 and ?DIC > 7 work best in the conditions and models tested here to maintain low false detection rates and misspecified model selection rates, respectively. The recommendations provided in this study will help researchers evaluate their models in a Bayesian SEM analysis and set the stage for future development and evaluation of Bayesian SEM fit indices. 相似文献
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雷桂媛 《浙江大学学报(A卷英文版)》2002,3(3):339-343
The rejection sampling method is one of the most popular methods used in Monte Carlo methods. It turns out that the standard rejection method is closely related to the problem of quasi-Monte Carlo integration of characteristic functions, whose accuracy may be lost due to the discontinuity of the characteristic functions. We proposed a B-splines smoothed rejection sampling method, which smoothed the characteristic function by B-splines smoothing technique without changing the integral quantity. Numerical experiments showed that the convergence rate of nearly O(N-1) is regained by using the B-splines smoothed rejection method in importance sampling. 相似文献
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Opticalcoherencetomography (OCT)wasorigi nallydevelopedforimagingintransparenttissue[1] .Since1 995 ,OCThasbeenadvancedtoimagefromophthal mologytonontransparenttissuewithahighimagingres olution[2 ,3 ] .OCTdemonstratesitsgreatestpotentialinsituationswhereconventionalbiopsyiseitherdangerousorineffective[4] .Becauseofthecomplexityofthelightpropagationinnontransparenttissue,theapplicationofOCTinhighlyscatteringbiologicaltissuesuchasskintis suearenotoptimistic.Yadlowsky[5] explainedthatmul tip… 相似文献
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用蒙特卡罗方法计算圆周率的近似值 总被引：1，自引：1，他引：0
何光 《内江师范学院学报》2008,23(4):14-16
利用随机数的思想,讨论了蒙特卡罗方法在具体问题中的应用,介绍了三种计算圆周率的近似值的方法;通过软件编程模拟实验过程,突出了蒙特卡罗法的特点． 相似文献
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兰小刚 《绵阳师范学院学报》2007,26(8):48-51,60
采用CORSIKA中的QGSJET强相互作用模型产生Monte Carlo的EAS事例样本,让所有Monte Carlo事例通过探测器阵列,形成Monte Carlo的观测事例样本。结果证实:通过研究宇宙线高能族事例发展,可以得到较理想的朝前区强子相互作用信息,从而能够有效的对目前正在使用的各种唯象模型的朝前区强子作用性质从TeV能区进行检验。 相似文献